Question 301000: the perimeter of a rectangle is 64 cm. the length is 4 less than twice the width. find the length and width Answer by Deina(147) (Show Source):
What do we know? We know that:
p = 64 cm
l = 2w - 4
and finally we know that
p = 2(l + w) or 2l + 2w
so we will substitute 2w - 4 for l in the formula:
p = 2(2w - 4) + 2w
Now we will distribute:
p = 4w - 8 + 2w
combine like terms:
p = 6w - 8
I like working on the left, so we'll flip-flop (advanced mathematical term) and replace "p" with 64:
6w - 8 = 64
Add 8 to each side:
6w = 72
divide each side by 6: so
w = 12
now remember that l = 2w - 4, and substitute 12 for 'w'
l = 20
Your answers are
Length = 20 cm
Width = 12 cm & bob's your uncle!
